This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Trauma is a well-recognized cause of hypopituitarism. Fifteen to twenty percent of adults who suffer a traumatic brain injury (TBI) that requires hospitalization and rehabilitation have been found to have growth hormone (GH) deficiency by GH stimulation testing. Moreover, abnormalities have also been established for the cortisol and thyroid axis. The hypothesis of this proposal is that hormone replacement in TBI patients with documented abnormalities in the GH, thyroid, or cortisol axis will improve muscle function, body composition, aerobic capacity (GH) and performance in tests of neuropsychologic function (GH, thyroid, cortisol). The Aims of this study are to: 1) determine the effect of thyroid hormone replacement on neuropsychologic function in subjects with TBI, 2) determine the effect of cortisol replacement on neuropsychologic function in subjects with TBI, and 3) determine the effect of recombinant human growth hormone (rhGH) on muscle function, body composition, aerobic capacity, and neuropsychologic function in subjects with TBI. Study sites will include, the General Clinical research center at U.T.M.B. in Galveston, the Transitional Learning Center (TLC) in Galveston, and at The Institute for Research and Rehabilitation (TIRR) in Houston. Activities specifically conducted at the GCRC in Galveston will include aerobic capacity testing, strength testing, body composition analysis, and muscle biopsies on the growth hormone treatment group.